Flavonoids from the grains of C1/R-S transgenic rice, the transgenic Oryza sativa spp. japonica, and their radical scavenging activities

Abstract

The transgenic rice cultivar of Oryza sativa spp. japonica cv. Hwa-Young, C1/R-S transgenic rice (C1/R-S rice), is a flavonoid-rich cultivar of rice. The grains of C1/R-S rice were extracted with aqueous MeOH, and the concentrated extract was partitioned with EtOAc, n-BuOH, and H2O, successively. Repeated silica gel, octadecyl silica gel (ODS), and Sephadex LH-20 column chromatographies for the EtOAc and n-BuOH fractions afforded four new flavonoids (compounds 2, 3, 7, and 8) along with four known flavonoids: (+)-3′-O-methyltaxifolin (1), brassicin (4), isorhamnetin-4′-O- β-d-glucosyranoside (5), and 3′-O-methyltaxifolin-5-O-β-d- glucopyranoside (6). The new flavonoids were identified as 3′-O- methyltaxifolin-7-O-β-d-glucopyranoside (2), 3′-O-methyltaxifolin- 4′-O-β-d-glucopyranoside (3), isorhamnetin-7-O-β-d-cellobioside (brassicin-4″-O-β-d-glucopyranoside) (7), and brassicin-4′-O- β-d-glucosyranoside (8) from the result of spectroscopic data including nuclear magnetic resonance spectrometry (NMR), mass spectrometry (MS), and infrared spectroscopy (IR). Also, quantitative analysis of major flavonoids (compounds 2, 3, and 8) in C1/R-S rice, O. sativa spp. japonica cv. Hwa-Young (HY), and a hybrid of two cultivar (C1/R-S rice/HY) extracts was performed using HPLC experiment. The isolated flavonoids were evaluated for their radical-scavenging effect on DPPH and ABTS radicals.